A conventional padlock generally includes a lock body, a locking device and a shackle so as to lock an object, as disclosed in U.S. Pat. Nos. 4,751,830 and 6,539,761. Another conventional padlock not only includes a lock body, a dual locking device and a shackle, but also includes a block member to retain or to release the shackle, also as disclosed in U.S. Pat. No. 6,848,283 and U.S. Patent Publication Nos. 2002/0088256, 2004/0226323 and 2004/0226324. The block member of the conventional padlock is mainly arranged for the dual locking device, especially for a key locking device as so to controlling movements of the shackle. However, connections between the block member and the dual locking device are arranged to be complicated. Therefore, an improved padlock is in great demand.